In recent years, in order to cope with strict emission standards set on internal combustion engines, it is necessary to promote the activation of an exhaust gas purifying device at the start of an internal combustion engine, maintain its active state during the operation of the internal combustion engine, and so on. In this respect, Patent Literature 1 and the like propose internal combustion engines in which an exhaust gas heating apparatus is incorporated in an exhaust passage upstream of an exhaust gas purifying device. This exhaust gas heating apparatus generates heated gas within exhaust gas and supplies this generated heated gas within exhaust gas and supplies this generated heating gas into the exhaust gas purifying device disposed downstream, to thus promote the activation of the exhaust gas purifying device and maintain its active state. To do so, the exhaust gas heating apparatus generally includes a fuel addition valve which adds fuel to the exhaust passage, and an igniting device such as a glow plug which heats and ignites the fuel to generate heated gas.
It is important to grasp the ignition status of the fuel added to the exhaust passage in the above-described exhaust gas heating apparatus. It may be desirable to stop the operation, as required, even during the operation of the exhaust gas heating apparatus. However, the conventional exhaust gas heating apparatus cannot meet the demand.
An intake air heating apparatus for use in an internal combustion engine or the like disclosed in Patent Literature 2 or Patent Literature 3 is adopted to detect an ignition temperature of fuel added to a combustor, and then, to determine a flame failure in the case where the detected temperature is lower than a predetermined value, thereby stopping fuel addition to the combustor.